Starting and operating device for electric discharge lamp



June 7, 1960 K. LARCHE ET AL 2,940,009

STARTING AND OPERATING DEVICE FOR ELECTRIC DISCHARGE LAMP Filed Oct. 10, 1956 FIG. 2

. IINVENTORS W j/bvb United States Patent STARTING AND OPERATING DEVICE FOR ELECTRIC DISCHARGE LAMP Kurt Larch and Werner Tillack, Berlin, Germany, as-

slgnors to Patent-Ireuhand-Gesellschaft fiir elektrisclre Gluhlampen m.b.H., Munich, Germany Filed Oct. 10, 1956, Ser. No. 615,165 Claims priority, application Germany Oct. 18, 1955 Claims. (Cl. 315-101) This invention relates to a starting and operating device for gaseous electric discharge lamps, more particularly to fluorescent lamps, in the bridge circuit of the preheatable incandescent electrodes of which a glow Switch is connected in series with a thermostatic switch. Well known designs of connecting in series a glow switch with a thermostatic switch do, up to the present, not ofier a suitable starting and operating device for electric discharge lamps because the following drawbacks have been found in the design of both the aforesaid switching elements. The glow switch used hitherto makes already, as it is known from the usual glow switch starter, several contact closures at closing and causes thereby several voltage impulses which, however, do not start the lamp but which impair its electrodes. Sometimes it happens that the glow switch remains in a closed position beyond the opening time of the thermostatic switch so that the fluorescent lamp extinguishes shortly after having started. Such and other faults have, hitherto,

hindered the use of combined thermostatic and glow switches connected in series in practice.

The aforesaid drawbacks are, according to the present invention, prevented in starting and operating devices of the above kind in such a manner that the glow switch is designed for an impulse voltage which is lower than that voltage required for starting the arc discharge in a fluo- ,rescent lamp with cold electrodes. to be. started whereas the thermostatic switch brings about an impulse voltage abovethe starting voltage of a fluorescent lamp with preheatable electrodes. By rating the glow switch in the aforesaid manner it is prevented that voltage impulses caused already by bad contact making when the glow switch is closed are brought about in the connected fluo- 'rescent lamp which voltage impulses have, as it is well known, a very bad influence upon electrodes when they are still cold.

To obtain a perfect operation of the combined starter according to the present invention it is, furthermore, suitable to design the glow switch for the special characteristics of a short closing time, a suficient contact-point pressure and particularly a low impulse voltage of preferably about 400 volts and to design the thermostatic switch for a high opening speed, a higher impulse voltage and a slow cooling. Consequently, the bimetallic strip of the glow switch has a thickness of preferably 0.2 mm. or less and a length of preferably 14 mm. or less and a filling pressure of Ne or A with small additions of H or N3 amounting preferably to more than 40 mm. Hg whereas the bimetallic strip of the thermostatic switch has a greater or at least the same thickness and a smaller or at most the same thickness and a smaller or at most the same length as the bimetallic strip of the glow switch and is filled with Ne with smaller additions of H or N of preferably 10 mm. Hg or less. A very favorable rating of the starting switches consists in providing the glow switch with a bimetallic strip of about 0.08-2.5-12

mm. and a gas filling of neon+ 1.0% H at a filling pressure of about 65 m. Hg whereas the thermostatic ICE switch has a bimetallic strip of about 0.12-3-12 mm. and approximately the same gas filling as the glow switch at a filling pressure of about 2 mm. Hg. If both the switching elements are rated in such a different manner it is obtained that the glow switch closes its contact in the shortest possible time after applying the line voltage. By means of the high filling pressure of the glow switch of more than 40 mm. Hg together with the symmetrical construction of its electrodes it is obtained that even in case of a bad contact a suific'i'ent impulse voltage for starting the discharge lamp is not produced at that moment at which the glow switch closes, at which moment the electrodes are still cold. In case of usual fluorescent lamps of 40 watts and a length of 1.20 m. the voltage required for starting the "arc discharge with cold electrodes lies for instance above 500 volts. If the glow switch is rated in the above mentioned manner it produces only an impulse voltage of about 400 volts so that undesired cold startings of the discharge lamp are prevented with safety. Thats particularly the case because the energy of the voltage impulse of the glow switch is very low in the present case because of the short opening time and remains without any remarkable efiect upon the lamp.

The heating coil of the thermostatic switch has, suitably, the same heating, speed as the electrode coils of the discharge lamp so that the. contact of the thermostatic switch is opened when the electrode coil has obtained the proper emission temperature.

trode coils of the discharge lamp. They from the same coil and differ only in their lengths.

After the glow switch contact has closed the bimetal 1. of the thermostatic switch is heated quickly: by means ofthe high capacity of the heating coil which is, suit= ofthe thermostatic switch itsbimetal has taken up a: greater quantity of heat than the;bime'tallic strip of'the' glow switch. By this means the thermostatic-switch :cbn-.- tact-returns slower into-the. closed position ofrest than the glow switch contact returns into the opened position. In order to obtain a very low impulse voltage when the glow. switch opens andia very-high impulse voltage when'the-thermostatic switch opens the additional heat ing. source of the glow switch should beconnectedto the counter contact of the bimetallicstrip and the heatingsource of the thermostatic switch to, the bimetallic strip itself. It is obtained thereby that in the glow switch the electrode surfaces have the same dimensions on both the sides ofthe contacts and bring about low impulse voltages whereas the thermostatic switch starter operating at the moment of contact-opening similar to a glow switch starter in a gaseous atmosphere makes occur highimpulse voltages in consequence of therectifier effect happening in because of the dissymmetry of the electrode surfaces. By this meansthereareobtained at the same time in the glow switch t gfinitedistances of theglow paths because the unmovable part of the bimetallic'strip forms the one electrode and the coil holders formtlre other glow electrode which are arranged in av constant distance from eachother. A- radio interference SUPPIQS'. sion capacitor causes in normal glow switches aeslight weldingof the contactswhereby-the time of closing-, and,- therewith, preheating of the electrode coils is prolongated,

Suitably, the heating coili of the thermostatic switch has the same characteristics. with regard to material, diameter and pitch as the elecmaybe cut:

be it not very exact. V Incombined starters of a thermoi to 1000 ohms, preferablyofaboutSOO ohms. By this means the discharge current'impulse of the condenser across the contacts of the glow switch is so weakened that a welding does no more occur. Preferably, the glow switch and the thermostatic switch,'if desired together with the suppression 'capacitorbridging the starters and "the damping resistor, are placed in a common protective casing thus permitting an easy insertion or a quick exchange of the 'double starter as incase of the well known simple glow switch'starter. A further improvement in starting a discharge lamp operated in the aforesaid'way maybe obtained in such a manner that the lamp is pro" v vided with an igniting strip extending over nearly the whole length of the lamp, suitably connected to an elec' 'trode across a resistor. Finally', the starting and opcrating device as described in the present invention may a 0.12-3-12 mm. For both the switches there has been be also operated in a bridge connection in which the incandescent electrodes of the lampare connected across a choke'coil and perhaps a condenser to the line voltage in such a manner that there is provided in the bridge circuit containing the glow switch and the thermostatic switch an additional counter-winding coupled with the choke coil in such a manner that this counter-winding diminishes the apparent resistance ofthe whole preheating circuit. By means of this well known arrangement .of a counter. winding coupled with the choke coil the preheating current of the'lamp electrodes is much ining of the lamp is guaranteed also in very cold weather I V In this'lattercase it is suitable to construct the starter as a safety starter, i.e. to build-in' a further contact which interrupts the bridge circuit if the starter operates for a creased and the timeof starting is shortened,'i.e. 'startlonger time, perhaps for 10 sec.,'for instance if the lamp is impaired or is not in operating conditions, which safety starter may, afterwards, be closed by hand. The choke coil may also be provided with a thermoswitch which interrupts'the whole circuit if the overcurrent continues and prevents thereby an injury to the choke .coil by the high current brought about when the starter is closed.

If there are used choke coils with counter winding the current intensity during theheating' period may be in; creased by an appropriate rating of the counter winding to such a degree that the electrode obtains fractions of a second that temperature which is required for starting. In such a case that time in which the glow switch remains in a closed condition also without additional heating suffices for the starting process so that no 7 special heating of thebimetal of the glow switch is necessary. V I

One embodiment of the aforesaid starting and operating device according to the present invention is shown in the accompanying drawing. Fig. 1 is a schematic diagram of the starting, and operating circuit employing the device ofthe invention with a sectional view in elevation of the glow switch and the thermostatic switch. Fig.

2,940,009 I t l 4 thermore, there is provided in the bridge circuit an additional winding '14 coupled inductively with the choke coil 17. As long as the main switch 15 is open the contact of the glow switch 5 is open whereas the contact of the thermostatic switch 9 is closed. After closing the main switch 15 the contact of glow switch 5 is, as it is well known, closed due to the heat of the glow discharge. Thereupon the resistanceheating wire 6 goes on heating the bimetallic strip of glow switch 5 so that the glow switch remains in a closed condition as long the bimetallic contact of the thermostatic switch 9 will be opened by the effect of its heating coil 10. By this continuous heating of glow switch 5 after the bimetallic contact has closedthere is, consequently, obtained a longer preheating of the-incandescent'electrodes' 3. As to the dimensions of the-starters thefollowing values have proved favourable which'guarantee an exact operation of the starters; The bimetallic strip of the glow switch 5 has, in our example,.a crossilsection of 008-25 mm. and a 'lengthof 12 Thebimetallic strip of the thermostatic switch 9 'has the following dimensions:

Hg in case of the glow switch. The heating resistors of the thermostatic switch and of the glow switch are rated in a proportion of about 2:1 up to 3:1, that means the thermostatic switch has about 5 turns of a coiled coil whereas the glow switchihas only two turns with equal dimensions in all the other respects. Of course, it is quite pcssible'to match the starters to each other correspondingly by taking other dimensions for the bimetals, the heating coil and the gas'pressure' so that the aforesaid operation of the starters is guaranteed too.

' To facilitate breaking of the easy welding contacts of the glow-switch these contacts are made of molybdenum ,or a semi-conductor. One contact; may also consist of ,tacts have closed by means of the additional'heating element 6 and is kept closed thereby. In our example there is, for the purpose of'a symmetrical distribution of the 'starter'parts at both the sides of the contacts and, thereby, for the purpose of decreasing the impulse voltage, the additional heatingsource 6 of the glowQswitch 5 connectedjto the counter-contact 7 of the bimetallic 1 strip 8. Vice versa, the heatingelement 10 of the thermostatic switch 9 is' connected to the bimetallic strip 11 for the'purpose of an asymmetrical arrangement of the starter parts at both the sides of the contacts and, thereby,.for the purpose of supporting a higher impulse voltage.

f A furtherimprovement of preheating can according to the present invention, beobtained in such a manner 7 that the preheating current of the lamp electrodes 3 is 2 is a perspective view of device. Fig.1 shows a V discharge lamp to be started, more particularlyalowpressure fluorescent lamp, with luminescent coating '2 and preheatable electrodes 3 connected in series across abridge circuit 4. Furthermore, there lie'in'this bridge circuit 4 a glow switch 5 with a. resistance heating 'wire 6 and athermo'static'switch9 with'a heating resistor-10L The contacts of both the starting switchesis' and 9 are bridged by a suppressioncapacitor 12 of about 500010 10,000 picofarads to which, if desired, a 'dampin'g re,-

sistorf19 is connected in series, A series choke coil '13 serves, ask is well known, to limit the discharge current of lamp 1. If necessary, there is also provided a condenser 20 connected in series with one of the choking windings "in order to obtaina capacitiveireactance. Furincreased by using the additional winding 114, lf'the starting device contains only a choke coil 13 then the additional winding 14'must be wound in-a counter-clockwise direction to the choke winding so that'the inductance of both the windings is decreased. lithe/starting device contains still 'acapacity 20 connected 'in series with'the choke coil 13 then the additional winding14 must be wound in a clockwise direction to the. choke coil 13580 'thatin that case the inductance of the choke coil is increased by'the preheating current. In both the above cases thefapparent resistance of 'thewh'ole preheating circuit must be decreased by the additional' winding l4;

Afterthe thermostatic switch 9 has opened the contact and has started the lamp 1 then the came a ofthe'glow switch 5 opens also again and the contact of the thermostatic switch starter returns into the contact positienf Now, as it is well known, the lamp voltage does suifice to cause the glow switch to operate.

Fig. 2 shows the assembly of the glow switch 5, of the thermostatic switch 9, of the radio interference suppression capacitor 12 and of the damping resistor 19 on a common base plate 16 which all are covered by a common protective casing 17. Thereby the combined starter is assembled to a unity and is dimensioned in such a manner that it may be inserted into the same place and into the same sockets as the glow switch starters used hitherto. In our example shown in the drawing the lamp 1 is, furthermore, provided with an igniting strip 18 which is connected electrically to one of the incandescent electrodes 3. By means of this arrangement a further improvement of the starting is obtained as far as such an improvement should be required at lowtemperatures. The igniting strip 18 may be provided in a well known manner outside or inside the lamp bulb. Thus by means of the above described and represented starting and operating device according to the present invention a sufficient, prolongated preheating of the lamp electrodes with an increased preheating current is obtained so that a quick and flickering-free starting takes place in a reliable manner even at low temperature.

What we claim as new and desire to secure by Letters Patent of the United States is:

l. A device for starting and operating a gaseous electric discharge lamp, more particularly of the fluorescent type, with two filamentary electrodes, comprising a glow switch and a thermostatic switch connected in electrical series relation with each other and with said filamentary electrodes forming a heating circuit for said filamentary electrodes, said glow switch having normally separated contacts and being operable to close the heating circuit for said filamentary electrodes upon application of a potential thereto, said glow switch being designed to re main closed under the action of the current flow through said heating circuit, said thermostatic switch having normally closed contacts operable to open following operation of said glow switch and to interrupt said heating circuit for said filamentary electrodes causing a high transient voltage above the voltage necessary for initiating a discharge in said lamp, said glow switch being so constructed and dimensioned to secure the transient voltage, caused by opening said glow switch contacts and thereby interrupting said heating circuit to be so low that initiating of a discharge between the cold electrodesin said lamp is prevented in a reliable manner.

2. A device for starting and operating a gaseous electric discharge lamp, more particularly of the fluorescent type, with two filamentary electrodes, comprising a glow switch and a thermostatic switch connected in electrical series relation with each other and with said filamentary electrodes forming a heating circuit for said filamentary electrodes, said glow switch having a gaseous medium of neon with small additions of hydrogen therein, the filling pressure of which is more than 40 mm. Hg and normally separated contacts, at least one of said contacts being a bimetallic strip of 0.2 mm. maximum thickness and 14 mm. maximum length which deflects into engagement with sufiicient contact point pressure with the other of said contacts upon heating by the initially occurred glow discharge, thereby extinguishing the glow discharge and closing the heating circuit for said filamentary electrodes, said glow switch being designed to remain closed under the action of the current flow through said heating circuit, said glow switch securing by its structure and dimensioning the transient voltage,

not

caused by opening said glow switch contacts in case of bad contacting and thereby interrupting said heating circuit, to be so low as approximately 400 volts thatinitiating of a discharge between the cold electrodes in said lamp is prevented with guaranty, said thermostatic switch having a gaseous medium of neon with small additions of hydrogen therein, the filling pressure of which is 10 Hg at the most, and being provided with a heater element and having normally closed contacts to complete the heating circuit for said filamentary electrodes, at least one of said contacts being a bimetallic strip the ruinimurn thickness and the maximum length of which is like said bimetallic strip of said glow switch said thermostatic switch opens contacts with high opening speed upon heating by said heater element after closing of the glow switch contacts, thereby interrupting said heating circuit for said filamentary electrodes causing a high transient voltage above the voltage necessary for initiating a discharge in said lamp.

3. A device for starting and operating a gaseous electric discharge lamp, more particularlyv of the fluorescent type, with two filamentary electrodes, comprising a glow switch and a thermostatic switch connected in electrical series relation with each other and with said filamentary electrodes forming a heating circuit for said filamentary electrodes, said glow switch having a gaseous of neon with an addition of 10% hydrogen therein, the filling pressure of which is approximately 65 and normally separated contacts, at least one of said con tacts being a bimetallic strip of 0.08 mm. thickness and 2.5 mm. width and 12 mm. length which deflects into engagement with sufiicient contact point pressure with the other of said contacts upon heating by the initially occurred glow discharge, thereby extinguishing the glow discharge and closing the heating circuit for said filamentary electrodes, said glow switch being designed to remain closed under the action of the current flow through said heating circuit, said glow switch securing by its'structure and dimensioning the transient voltage, caused by opening said glow switch contacts in case of badcontacting and thereby interrupting said heating circuit, to' be so low that initiating of a discharge between the cold electrodes in said lamp is prevented with guaranty, said thermostatic switch having a gaseous medium of'neon with an addition of 10% hydrogen therein, the filling pressure of which is approximately 2 mm. Hg, and being provided with a heater element and having normally closed contacts to complete the heating circuit for said 'filamen tary electrodes, at least one of said contacts being abi metallic strip of 0.12 mm. thickness and 3 mm. width and 12 mm. length said thermostatic switch opens contacts upon heating by said heater'element after closing of the glow switch contacts, thereby interrupting saidheating circuit for said filamentary electrode causing a high transient voltage above the voltage necessary for a discharge in said lamp.

4. A device for starting and operating a gaseous elec tric discharge lamp, more particularly of the fluorescent type, with two filamentary electrodes, comprising a glow switch and a thermostatic switch connected in electrical series relation with each other and with said filamentary electrodes forming a heating circuit for said filamentary electrodes, said glow switch having a gaseous medium of neon with small additions of hydrogen therein, the filling pressure of which is more than 40 mm. Hgfan'd normally separated contacts, at least one of said contacts being a bimetallic strip of 0.2 mm. maximum thick ness and 14 mm. maximum length which deflectsinto engagement with suificient contact point pressure with the other of said contacts upon heating by the initially occurred glow discharge, thereby extinguishing the glow discharge and closing the heating circuit for said filamentary electrodes, said glow, switch being designed to remain closed under the action of thecurrent flow through said heating circuit, said glow switch securing by its'struoture and dimensioning the transient voltage, caused by opening said glow switch contacts in case of bad contacting and thereby interruptingsaid heating circuit, to be so low as approximately 400 volts that initiating of a discharge between the cold electrodes in said lamp is prevented with guaranty, said thermostatic switch having a gaseous medium of neon with small additions of hydrogen therein, the filling pressure of which is 10 mm. Hg' at A switch securing by its structure I and 7 volts, that initiating of the, most, and being provided with a coiled heating vfilament of thesame material and the same dimensions as to diameter and pitch as said coiled filamentary electrodes,

, differing at the most in its length from that of said filaby interrupting said heating circuit for said filamentary electrodes causing a hightransient voltage'above the voltage necessary for initiating a discharge in said lamp.

7 5. A device for starting and operating a gaseous electric-discharge lamp, more particularly of the fluorescent type, with two filamentary electrodes, comprising 'a glow switch and a thermostatic switch'connected in electrical l seriesrelation 'with each other-and with said filamentary electrodes forming a heating circuit for said filamentary electrodes, said glow switch having normally separated contacts, at'leas t one of said contacts being abimetallic strip of 0.2 thickness and 14 mm. maximumlength which deflects into engagement with sufi ficient contact point pressure with the other of said contacts upon heating by'the initially occurred glow dis- "charge, thereby extinguishing the glow discharge and closingthe heating circuit for said filamentary electrodes, said glow switch being provided with aheater element connected in electrical series relation with said contacts and maintaining said bimetallic element under the action of the current flow through said heating circuitin a heated ,condition' and keeping said contacts closed, said glow switch securing by its structure and dimensioning the transient voltage, caused by opening said glow switch contacts in case of bad contacting and thereby interrupting said heating circuit, to be so low that initiating of a discharge between the cold electrodes in said lamp isprevented with guaranty, said thermostatic switch being provided with a heater element and having normally closed contacts to complete thefheating circuit for said filamentary electrodes, at least one 'of said contactsbeing 'a bimetallic'element which opens contacts uponheating' by said heater element after. closing of the glow switch contacts, thereby interrupting said heating circuit for said,

filamentary electrodes causing a high transient voltage tn'c discharge lamp, more particularly of the fluorescent type, with two filamentary electrodes, comprising a glow switch andzathermostatic switch connected in electrical series relationwith each other. and twith said filamentary electrodes forming a heating circuit for said filamentary electrodes, said glow switch having a gaseous medium of neon with small additions of hydrogen therein, the filling pressure of which is more than 40 mm. Hg,rand normallysepar ated contacts, at least one of said contacts being a; bimetallic strip of 0.2 mm. maximum thickness-and 14 mm. length which deflects into engagement with mostatic switch having a gaseous medium ofneon with small additions of hydrogen therein, the filling pressure of which is 10 mm. Hg at the most, and being provided with a heater element capable of at leastttwice the capacity loading of that of said glow switch heater element at the same current intensity, said thermostatic switch having normally closedcontacts tocomplete the heating circuit for said filamentary electrodes, at least one of said contacts being a bimetallic strip the minimum thickness and the maximum length of which is like said bimetallic strip of said glow switch, said thermostatic switch opens contacts with high opening speed upon heating by said heater element after closing the glow switch contacts, thereby jnterruptingsaid heating circuit'for said filamentary electrodes causing a high transient voltage above the voltage necessary for initiating a discharge in said lamp, i

7. A device for starting and operating a gaseous electric discharge lamp,"more particularly of the fluorescent type, with two filamentary electrodes, comprising alglow switch and a thermostatic switch connected in electrical series relation with each other and with said filamentary electrodes forming a heating circuit for said filamentary electrodes, said glow switch, having normally separated contacts, at least one of said contacts being a bimetallic strip 0120.2 mm. maximum thickness and 14 mm. maximum length which deflects into engagement withlsufiicient contact point pressure with. the other of said contacts upon heating by the initially occurred glow discharge thereby extinguishing the glow discharge and closing the heating circuit forsaid filamentary electrodes, said glow switch being provided with a heater element connected in electricalseries relation with the counter contact of said himetallic element and maintaining said bimetallic element under the action'of the current flow through said heating circuit in a heated condition and keeping said contacts closed, said glow switch securing by its structure and dimensioning the transient voltage, caused by opening said glow switch contacts in case of bad contacting and therebpvegthevoltagenecessaryfor initiating a discharge in 'saidlamp.

I 6. A device for'starting and'operatinga gaseous elecby interrupting said heating circuit, to be so low as approximately 400 volts that initiating of a discharge between the cold electrodes in'said lamp is prevented with guaranty, said thermostatic switch being provided with a heater element and having-normally closed contacts'to complete the heating circuit for said filamentary electrodes, at least one of said contacts being a bimetallic element connected in elect'rical series relation with said heater element, said therm'ostatic switch opens contacts upon heating by said heater element aftertclosing of the glow switch contacts, thereby interrupting said heating circuit for said filamentary electrodes causing a high transient voltage above the'voltage necessary for initiating a dis- A charge in said lamp.

sufiicienhcontact points pressure with the other of said contacts upon he'ating by theinitially'occurred glowdischarge, thereby extinguishing the glow discharge and closthe heating circuit for said filamentaryelectrodes, said glow switch being provided 7 nected'in electrical series relation with said contacts and maintainingsaid bimetallic element under the action of the rcurr ent flow through said heating circuitinaheated conditionqand keeping said contacts, closedgsaid glow with a heater element condim n on t transient voltage, caused by opening said glow switch nodes in said. lamp is w w tt l i "said glowswitch being 8. A device for starting and operating a gaseous electric discharge lamp, more particularly of the fluorescent type, with two filamentary electrodes, comprising a glow switch and a thermostatic switch connected in electrical series relation with each other and with said filamentary electrodes forming a heating circuit for said filamentary electrodes, and an ohmic resistance and a radio interference suppression capacitor connected in electrical series relation with each other and connected in parallel to said two switches, said ohmic resistance amountingto approximately 500 ohms, said glow switch having normally separated contacts, at least one of said contacts being a bimetallic strip of 0.2 mm. maximum thickness and 14 mm. maximum length which deflects into engagement with sufficient' contact point pressure with the other of sa d contacts upon heating bythe initially occurted' glow discharge, thereby extinguishing the glow discharge and closing the heating circuit for said'filamentary electrodes, designed to remainwclosed under the action of the current flow through said heating circuit, s aid glow switch securing by its structure and dimension- 'ing the transient voltage, caused by opening said glow switch contacts in case of bad contacting and thereby interrupting said heating circuit, to be so lowas approximately 400 volts, that initiating of a discharge between the cold electrodes in said lamp is prevented with guaranty, said thermostatic switch being provided with a heater element and having normally closed contacts to complete the heating circuit for said filamentary electrodes, at least one of said contacts being a bimetallic element, said thermostatic switch opens contacts upon heating by said heater element after closing of the glow switch contacts, thereby interrupting said heating circuit for said filamentary electrodes causing a high transient Voltage above the voltage necessary for initiating a discharge in said lamp.

9. A device for starting and operating a gaseous electric discharge lamp, more particularly of the fluorescent type, with two filamentary electrodes, comprising a glow switch and a thermostatic switch connected in electrical series relation with each other and with said filamentary electrodes forming a heating circuit for said filamentary electrodes, and an ohmic resistance and a radio interference suppression capacitor connected in electrical series relation with each other and connected in parallel to said glow switch, said ohmic resistance amounting to approximately 500 ohms, said glow switch having normally separated contacts, at least one of said contacts being a bimetallic strip of 0.2 mm. maximum thickness and 14 mm. maximum length which deflects into engagement with sufficient contact point pressure with the other of said contacts upon heating by the initially occurred glow discharge, thereby extinguishing the glow discharge and closing the heating circuit for said filamentary electrodes, said glow switch being designed to remain closed under the action of the current flow through said heating circuit, said glow switch seeming by its structure and dimensioning the transient voltage, caused by opening said glow switch contacts in case of bad contacting and thereby interrupting said heating circuit, to be so low as approximately 400 volts, that initiating of a discharge between the cold electrodes in said lamp is prevented with guaranty, said thermostatic switch being provided with a heater element and having normally closed contacts to complete the heating circuit for said filamentary electrodes, at least one of said contacts being a bimetallic element, said thermostatic switch opens contacts upon heating by said heater element after closing of the glow switch contacts, thereby interrupting said heating circuit for said filamentary electrodes causing a high transient voltage above I thevoltage necessary for initiating a discharge in said lamp.

10. A device for starting and operating a gaseous electric discharge lamp, more particularly of the fluorescent type, with two filamentary electrodes, comprising a glow switch and a thermostatic switch connected in electrical series relation with each other and with said filamentary electrodes forming a heating circuit for said filamentary electrodes, said glow switch having a gaseous medium of argon with small additions of hydrogen therein, the filling pressure of which is more than mm. Hg and normally separated contacts, at least one of said contacts being a bi-v metallic strip of 0.2 mm. maximum thickness and 14 mm. maximum length which deflects into engagement with sufficient contact point pressure with the other of said contacts upon heating by the initially occurred glow discharge, thereby extinguishing the glow discharge and closing the heating circuit for said filamentary electrodes, said glow switch being designed to remain closed under the action of the current flow through said heating circuit, said glow switch securing by its structure and dimensioning the transient voltage, caused by opening said glow switch contacts in case of bad contacting and thereby interrupting said heating circuit, to be so low as approximately 400 volts that initiating of a discharge between the cold electrodes in said lamp is prevented with guaranty, said thermostatic switch having a gaseous medium of neon with small additions of hydrogen therein, the filling pressure of which is 10 mm. Hg at the most, and being provided with a heater element and having normally closed contacts to complete the heating circuit for said filamentary electrodes, at least one of said contacts being a bimetallic strip the minimum thickness and the maximum length of which is like said bimetallic strip of said glow switch, said thermostatic switch opens contacts with high opening speed upon heating by said heater ele ment after closing of the glow switch contacts, thereby interrupting said heating circuit for said filamentary electrodes causing a high transient voltage above the voltage necessary for initiating a discharge iri said lamp.

Abbott Dec. 30, 1941 Hodgkins May 14, 1946 

